Climate Change's Effect on Migration

Image by Joel Sartore. Blog by Lucy Slater

Migration occurs across a huge range of species, from birds to frogs, sardines to butterflies, and antelope to turtles, to name a few. These movements may be to seek new food sources, more tolerable winter conditions, or to breed and rear young. Whatever the reason though, migration is important.

Global warming and migration

Global warming has been accelerating over the last few decades and this is starting to have an effect on migration, which many believe to be negative. Migration is usually triggered by a combination of climate related factors, such as sunlight levels and temperature, and due to warming temperatures seen earlier in the year, these migrations are starting earlier.

What could this mean?

Migration is a huge undertaking, often seeing species travel thousands of miles. The arctic tern, for example, flies from the Arctic to the Antarctic and back again each year! Finding enough food to fuel these journeys is paramount and migrations are therefore synchronised to food availability, both during the journey and once they reach their destination. With migration patterns changing, these migrants may miss essential food sources, which in turn could result in a marked decrease in their survival and breeding success.

Species such as the hummingbird are particularly vulnerable due to their high metabolism. Hummingbird flight is extremely labour intensive and they must feed every few hours or they die. If they mistime their migration and miss when plants are flowering, the nectar they feed on will be unavailable.

The house of cards tumbles

Relationships between species within ecosystems are complex and each species plays an important role. When one species is affected, the knock-on effect can be significant. Many migrations are a huge food source for predators. The sardine run for example, feeds thousands of dolphins, sharks, whales and predatory fish. But this migration is also triggered by environmental cues and if the sardine run ceases due to global warming, a massive food source will be extinguished.

Pollinators such as the monarch butterfly also migrate. If their migrations are not timed correctly, plants will loose their pollinators. Without the ability to reproduce the very foundations of food chains in these ecosystems are at risk as are all the species which feed on them.

Predators migrate too, whales move to new feeding grounds each year and consume huge numbers of fish, plankton and krill. However, due to climate change, some species such as right whales are abandoning their traditional feeding grounds. The prey population, which would normally be kept in check by the whales, could grow exponentially and a result, over-exploit their own food sources, which could exhaust the ecosystem.

Due to the complexity and extensive distances covered by migration, research is difficult to undertake and is still a relatively new area of study. Therefore, the effects global warming could have on this phenomenon are still not fully understood.

We still have time to stop these things getting worse, so let’s keep pushing to protect our amazing world from climate change.

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